The amount of money you can make from placing articles and affiliate links on your site differs from one person to another. The amount that you can make will mostly depend on how successful your site it. What determines the success of your website? Good search engine rankings, making an enjoyable and informative site, niches, etc...
People have claimed to make as much as $10,000 p/month with article and affiliate marketing this is not the norm. Most people just starting out can expect to make anywhere from $500 - $1000 p/month. If you are expecting to make this amount of money on a recurring basis you will need to continually work on your site.
When you have achieved success with one site, don't stop there continue to build more niche sites. The more niche sites that you have the better your income will be. After, you have completed your first site which is the hardest creating additional niche sites should be rather easy.
Another, problem faced by internet entrepreneurs is finding affiliates for their niche sites. The most important thing to know when trying to overcome this obstacle is where to look, what to look for, etc... Where to look is pretty easy you can just do a search on Google (affiliate programs) to find some good affiliate sites. What to look for is another story.
When looking at an affiliate program that you are planning to promote you will want to look for certain things to determine if the product will be profitable for you. There are several types of affiliates and some will offer you more money from a sale than others. Before you get hazy-eyed by dollar signs, however, remember some products are bound to sell more than others. If you sell one product four times a year from a little known company that gives you $100 per sale or sell a well known product 3 times a week at the rate of $10 per sale, then you will make much more money with the $10 per sale product. Often times large well known companies will offer a very small profit per sale because they are established and know that their product is likely to sell well. Small, unknown companies, on the other hand, need all of the promotion they can get. Also, because they are unknown, their products are likely to sell less frequently.
Always, remember to have relevant affiliate products on your niche site(s). You do not want to promote fast cars on a site that is for parents of young children. While some of those visitors to your site might be interested in fast cars most will not be. If your niche site targets parents of young children, then promote baby products. If you niche site targets gardeners, then promote gardening products. If you promote baby products to gardeners, you are almost guaranteed to not make a profit no matter how much money the affiliate company offers for a sale.
Lastly, The amount of money that you make online is entirely in your hands. It is based primarily on how diligent, focused, and committed you are to making it online. Know this and know it well many online ventures do not work mostly because the venturer is not willing to do what it takes to make it.